Rubber vibration isolator with bracket and method of manufacturing the same

Abstract: A rubber vibration isolator with a bracket (10) and a method of manufacturing the same. An elastic rubber member (22) is vulcanization bonded to both a metallic cylindrical portion (11) and an inner sleeve (21) disposed inside of the cylindrical portion in a first securing portion (22a,22b) opposed to an inner surface of the metallic cylindrical portion (11) and a second securing portion (25) opposed to an outer surface of the inner sleeve (21). Next, the metallic cylindrical portion (11) is plastically deformed towards an axial center thereof to precompress the elastic rubber member (22). An arm portion (12) is secured to an outer surface of the plastically deformed cylindrical portion (11) by low temperature welding, thereby forming the bracket (10).

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a rubber vibration isolator provided with a bracket, especially to a bracket according to the preamble of the patent claim 1, and methods of manufacturing the same. Description of Related Art One example of a conventional cylindrical engine mount needing a bracket is illustrated in FIGS. 10 through 14 which represent the closest prior art to the invention and which show a bracket known from JP-57-94 146 in a simplified structure. In order to manufacture the above-described conventional engine mount, as shown in FIGS. 10 to 12, a cylindrical rubber vibration isolator 50 composed of an inner sleeve 51, an outer sleeve 52 and an elastic rubber member 53 bonded to the inner sleeve 51 and the outer sleeve 52 by vulcanization is first formed by using a mold, and then, the durability of the elastic rubber member 53 is improved by drawing the cylindrical rubber vibration isolator 50 from the outside of the outer sleeve 52. Upon drawing, the outer sleeve 52 is plastically deformed to reduce the diameter thereof, thereby precompressing the elastic rubber member 53. Thus, as shown in FIGS. 12, a drawn cylindrical rubber vibration isolator 50' is prepared. As shown in FIG. 13, a bracket 60 made of steel is also prepared by integrally securing an arm portion 62 to a cylindrical portion 61 in an arc-shaped portion 63 by spot welding, arc welding or other electrically welding method. By press-fitting the drawn cylindrical rubber vibration isolator 50' in the cylindrical portion 61 of the thus prepared bracket 60, the engine mount provided with a bracket (FIG. 14) is obtained. This conventional rubber vibration isolator with a bracket, however, has problems that the outer sleeve 52 is needed as an essential component and that the process of press-fitting the drawn cylindrical rubber vibration isolator 50' in the cylindrical portion 61 of the bracket 60 is also needed. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a bracket with a rubber vibration isolator, which does not need any outer sleeve, and an improved method of manufacturing such a bracket without the press-fitting process of the cylindrical rubber vibration isolator in the hollow cylindrical portion of the bracket. This object is solved by a bracket having the technical features according to the enclosed patent claim 1 and by methods according to the patent claims 4 and 7, respectively. According to claim 8, welding the cylindrical portion and the arm portion is carried out by resistance welding. In order to prevent the degradation of the elastic rubber member due to heat upon welding, the surface temperature of the cylindrical portion contacting with the elastic rubber member must be controlled to 150°C or less, preferably 130°C or less. To this end, it is necessary to feed a large amount of current for a short time and then immediately cool the cylindrical portion. In addition, it is preferable to project one of abutting faces of the cylindrical portion and the arm portion to be welded and concentrate welding current only in the projected abutting faces. With this arrangement, the total amount of necessary welding current can be decreased and heat generation due to welding current can be reduced. With the bracket of the present invention, the elastic rubber member has the first securing portion secured to the inner surface of the cylindrical portion of the bracket and the second securing portion integrally bonded to the outer surface of the inner sleeve by vulcanization, and is retained between the cylindrical portion and the inner sleeve in the precompressed state. Therefore, good vibration isolating function substantially identical to that of the conventional arrangement is obtained. Furthermore, since the bracket is formed by securing the metallic arm portion to the outer surface of the cylindrical portion by welding, such an outer sleeve as required by the conventional arrangement is not needed. With the method of the present invention according to claim 4, after the metallic cylindrical portion of the vulcanized molded body is drawn, the metallic arm portion is secured to the outer surface of the cylindrical portion by resistance welding. Therefore, the elastic rubber member can be precompressed similarly to that of the conventional arrangement. Furthermore, the cylindrical portion also has a function identical to that of the outer sleeve of the conventional arrangement. Therefore, the outer sleeve is not needed, and accordingly, it is unnecessary to press-fit the rubber vibration isolator in the cylindrical portion. With the method of the present invention according to claim 7, by virtue of the process of forcibly bringing the opposed free edges of the cylindrical portion of the vulcanized molded body close to each other, the elastic rubber member can be precompressed. And in order to maintain this precompressed state, the arm portion is secured to the cylindrical portion so as to connect the opposed free edges thereof by welding, preferably by resistance welding. As a result, the cylindrical portion without free edges is obtained, and the precompression of the elastic rubber member is ensured. As a further technical background of the invention the following documents are briefly discussed : The reference EP 0 529 629 A1 shows a trailing arm comprising an arm portion in which a bore is formed. Furthermore, a rubber vibration isolator (bushing) consisting of an inner sleeve, an outer sleeve and a rubber member is fitted in said bore. According to the reference FR 2 292 153, an outer sleeve of a rubber vibration isolator is directly secured to the axial end of a rod by welding. However, this welding process obviously takes place before the rubber is fitted in the outer sleeve. Moreover, the rubber member is press-fitted within the outer sleeve and is additionally fixed in the axial direction of the vibration isolator by an inwardly directed projection of the outer sleeve. That is, the problems concerning the degradation of the elastic rubber member due to the resistant welding do not arise in reference FR 2 292 153, especially if the rubber member is bonded to the outer sleeve by vulcanization before the outer sleeve is welded to the arm portion. Other objects of the present invention will become apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation view of a first embodiment of a bracket provided with a rubber vibration isolator in accordance with the present invention; FIG. 2 is a side elevation view of the bracket of FIG. 1; FIG. 3 is a longitudinal sectional view of a vulcanized molded body which is shown for explaining a first embodiment of the method of manufacturing the bracket with a rubber vibration isolator of FIG.1; FIG. 4 is a front elevation view or a vulcanized molded body which is shown for explaining the first embodiment of the method of manufacturing the bracket with a rubber vibration isolator of FIG. 1; FIG. 5 is a front elevation view of a drawn vulcanized molded body obtained by drawing the vulcanized molded body of FIG. 3; FIG. 6 is a front elevation view of an arm portion of the bracket of FIG. 1; FIG. 7 is a front elevation view of another arm portion; FIG. 8 is a front elevation view of a vulcanized molded body of a second embodiment; FIG. 9 is a front elevation view of a second embodiment of a bracket with a rubber vibration isolator, which is formed by reducing the diameter of the cylindrical portion of the vulcanized molded body of FIG. 8, and welding abutting faces of the cylindrical portion and the arm portion to each other; FIG. 10 is a longitudinal sectional view of a conventional rubber vibration isolator which is not precompressed; FIG. 11 is a front elevation view of the conventional rubber vibration isolator which is not precompressed; FIG. 12 is a front elevation view of the conventional rubber vibration isolator which is in the precompressed state; FIG. 13 is a front elevation view of the conventional bracket not including the rubber vibration isolator; FIG. 14 is a front elevation view of the conventional bracket with a rubber vibration isolator. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the present invention will be explained with reference to FIGS. 1 through 9. First Embodiment FIGS. 1 through 6 illustrate a first embodiment 1 of the present invention. As shown in FIG. 1, a bracket 10 is composed of a cylindrical portion 11 of a ring-shaped cross-section and a plate-shaped arm portion 12. These portions 11 and 12 are both made of steel. A concavely curved arc-shaped end face 12a of the arm portion 12 abut a convexly curved arc-shaped outer surface 11a of the cylindrical portion 11, and abutting faces 30 of both the arm portion 12 and the cylindrical portion 11 are welded to each other. An inner sleeve 21 made of steel is disposed inside of the cylindrical portion 11 concentrically therewith, and a column-shaped elastic rubber member 22 is disposed in an annular space defined by the cylindrical portion 11 and the inner sleeve 21 to rectilinearly connect the cylindrical portion 11 and the inner sleeve 21 by vulcanization bonding. More specifically, the elastic rubber member 22 is integrally bonded to the inner surface of the cylindrical portion 11 on radially symmetrical left and right sides thereof in first securing portions 22a and 22b, and is also integrally bonded to the outer surface of the inner sleeve 21 in a second securing portion 25. Rubber stoppers made of the same rubber as that of the elastic rubber member 22 are vulcanization bonded to an inner surface of the cylindrical portion 11 so as to be spaced from the elastic rubber member 22 in the width direction thereof. The diameter of the cylindrical portion 11 of the bracket 10 is reduced by drawing the cylindrical portion 11 radially inwardly with respect to the inner sleeve 21 substantially with uniform, thereby precompressing the elastic rubber member 22. Thus, the elastic rubber member 22 in the precompressed state receives a shear load applied to the cylindrical portion 11 or the inner sleeve 21. Hereinafter, a first method of manufacturing a rubber vibration isolator with a bracket will be explained. First, the cylindrical portion 11 and the inner sleeve 21 are respectively prepared by cutting steel tubes of desired internal and external diameters into desired lengths. And the arm portion 12 (FIG. 6) is also prepared by bending a steel sheet. Next, the cylindrical portion 11 is placed within a mold cavity, and the inner sleeve 21 is places inside of the cylindrical portion 11. Then, a predetermined portion of a space defined by the cylindrical portion 11 and the inner sleeve 21 is filled with a rubber material, and the rubber material is vulcanized to form the elastic rubber member 22 and the rubber stoppers. As a result, as shown in FIGS. 3 and 4, the vulcanized molded body 20' wherein the vulcanized elastic rubber member 22 is integrally bonded to both the cylindrical portion 11 and the inner sleeve 21 by vulcanization is obtained. The cylindrical portion 11 of the vulcanized molded body 20' has an external diameter of 91mm and a width of 35mm. The cylindrical portion 11 of the vulcanized molded body 20' is drawn from the outside thereof towards the axial center thereof substantially with uniform by means of a well known drawing device (not shown). As a result, as shown in FIG. 5, the cylindrical portion 11 is plastically deformed such that the diameter thereof is reduced, and a drawn vulcanized molded body 20 of which the elastic rubber member 22 is in the precompressed state is obtained. Upon drawing, the external diameter of the cylindrical portion 11 is decreased to 85mm, and the width thereof is increased to 38mm. Then, concavely curved arc-shaped end faces 12a of the arm portion 12 (FIG. 6) are abutted on a convexly curved arc-shaped portion 11a of the lower part of the outer surface of the cylindrical portion 11, and the abutting faces 30 of the cylindrical portion 11 and the arm portion 12 are welded to each other by means of a resistance welding machine. Due to welding current, the abutting faces 30 are molten into each other, thereby integrally securing the cylindrical portion 11 and the arm portion 12 to form the bracket. Thus, the rubber vibration isolator with a bracket 1 illustrated in FIG. 1 is manufactured. The rubber vibration isolator with a bracket 1 of the present embodiment has vibration isolating properties identical to those of the conventional arrangement. In the present embodiment, the cylindrical portion 11 is formed by cutting a steel tube into a predetermined length. Instead, the cylindrical portion 11 can be formed by press-forming a sheet material into a cylindrical configuration. Furthermore, the concavely curved arc-shaped end faces 12a of the arm portion 12 may be formed irregular, as shown in FIG. 7. In this arrangement, resistance welding is carried out only in tip ends of projections of the irregular faces 12a so that the energy required for welding can be reduced. This results in the elastic rubber member 22 bonded to the inner surface of the cylindrical portion 11 being prevented from being degraded due to welding heat. The projections of the irregular faces 12a may have a trapezoidal cross-section. The number of the projections may be one or more. The entire faces 12a may be formed irregular, as shown in FIG. 7. Second Embodiment FIG. 9 illustrates a second embodiment 2 of the present invention. In the present embodiment, instead of the cylindrical portion 11 of the first embodiment, a cylindrical portion 111 of a configuration different from that of the cylindrical portion 11 is used. Namely, as shown in FIG. 8, the cylindrical portion 111 is formed by curving a sheet steel such that free edges 111a, 111b are opposed to each other through a gap 112, thereby having a C-shaped cross-section. The thus formed C-shaped cylindrical portion 111 is placed in a mold cavity, an inner sleeve 21 is placed inside of the cylindrical portion 111, the space defined by the C-shaped cylindrical portion 111 and the inner sleeve 21 is filled with a rubber material, and the rubber material is vulcanized. As a result, a vulcanized molded body 200' (FIG. 8) wherein a vulcanized elastic member 22 is integrally bonded to both the cylindrical portion 111 and the inner sleeve 21 is prepared. Next, by means of a gripping or fastening device (not shown), the opposed free edges 111a and 111b of the C-shaped cylindrical portion 111 are forcibly brought close to or into contact with each other to substantially reduce the diameter of the cylindrical portion 111. Then, as shown in FIG. 9, the concavely curved arc-shaped end faces 12a of the arm portion 12 are abutted on the lower part of the cylindrical portion 111 including the opposed free edges 111a and 111b. And both the abutting faces 31 on the side of the free edge 111a and the abutting faces 32 on the side of the free edge 111b are subjected to resistance welding by means of the above-described resistance welding device. Thus, the bracket 100 is formed, and accordingly the rubber vibration isolator with a bracket 2 is manufactured. In the present embodiment, by closing the open free edges of the C-shaped cylindrical portion 111, the elastic rubber member 22 can be precompressed towards an axial center thereof. And, by welding the arm portion 12 to the cylindrical portion 111 so as to connect these closed edges, securing the arm portion to the cylindrical portion and closing the cylindrical portion are both carried out at the same time. By virtue of resistance welding, the temperature of the cylindrical portion 111 contacting with the elastic rubber member 22 can be controlled to about 60 to 150°C in an atmosphere of 24°C, and accordingly, the vibration isolating properties of the elastic rubber member 22 are not deteriorated. Therefore, the rubber vibration isolator with a bracket 2 of the present embodiment has excellent vibration isolating capacity and durability similarly to those of the conventional arrangement. By virtue of resistance welding, the temperature of the cylindrical portion can be prevented from rising above 150°C. Therefore, the obtained bracket with a rubber vibration isolator can be semipermanently used for a motor vehicle, similarly to the conventional arrangements. The welding operation of the cylindrical portion and the arm portion is carried out by a resistance welding device manufactured at Banyou Kogyo Co., Ltd. Resistance welding enables securing the above-described portions without rising of the temperature of the cylindrical portion above 150°C due to heat upon welding, and accordingly the vibration isolating properties and durability suitable to the bracket with a rubber vibration isolator for use in a motor vehicle can be obtained. As described above, welding may be carried out such that the temperature of the cylindrical portion does not rise above 150°C. Therefore, other welding method such as arc welding is applicable provided that the temperature of the cylindrical portion can be prevented from rising by using a low temperature welding rod, or by welding in a liquid. In accordance with the present invention, the bracket with a rubber vibration isolator, which does not need any outer sleeve, and the improved method of manufacturing the same, which does not need the press-fitting process of the outer sleeve in the bracket, can be provided. Accordingly, production costs can be reduced, as compared with the conventional arrangement. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims: A bracket (10) comprising a hollow cylindrical portion (11) made of a metallic material and a metallic arm portion (12) extending from a single side of said cylindrical portion (11) and integrally secured to an outer surface of said cylindrical portion (11) by welding, wherein said cylindrical portion (11) forms an aperture accommodating a rubber vibration isolator composed of an inner sleeve (21) disposed inside an outer sleeve so as to face said outer sleeve with an annular space and an elastic rubber member (22) disposed in said annular space, said elastic rubber member (22) having a first securing portion (22a, 22b) bonded to an inner surface of said outer sleeve by vulcanization and a second securing portion (25) integrally bonded to an outer surface of said inner sleeve (21) by vulcanization and being in the precompressed state towards an axial center of said outer sleeve, characterized in that said hollow cylindrical portion (11) of said bracket (10) forms said outer sleeve wherein said first securing portion (22a, 22b) of the elastic rubber member (22) is directly bonded to the inner surface of said aperture. A bracket (10) according to claim 1, characterized in that said cylindrical portion (11) and said arm portion (12) are integrally welded to each other by resistance welding. A bracket (10) according to claim 1, characterized in that said cylindrical portion (11) is composed of a cylindrical sheet metal and obtained by bending a flat sheet metal. A method of manufacturing a bracket (10) according to one of the claims 1 to 3, comprising the steps of: placing said cylindrical portion (11) separate from said arm portion (12) within a cavity of a mold, placing said inner sleeve (21) inside of said cylindrical portion (11), filling a space defined by said cylindrical portion (11) and said inner sleeve (21) with a rubber material, and vulcanizing said rubber material so that a vulcanized elastic rubber member (22) is integrally bonded to both an inner surface of said cylindrical portion (11) and an outer surface of said inner sleeve (21) by vulcanization, thereby forming a vulcanized molded body; drawing said cylindrical portion (11) of said vulcanized molded body to plastically deform it towards an axial center thereof; and integrally securing said metallic arm portion (12) to an outer surface of said plastically deformed cylindrical portion (11) by welding to form said bracket (10) composed of said cylindrical portion (11) and said arm portion (12). A method according to claim 4, characterized in that said welding is carried out by resistance welding, said outer surface of said cylindrical portion (11) and said metallic arm portion (12) being relatively abutted on each other, and a welding current being fed to abutting faces of said cylindrical portion (11) and said arm portion (12) to be molten into each other. A method according to claim 5, characterized in that said welding is carried out such that the temperature of said cylindrical portion (11) is controlled to 150°C or less upon welding. A method of manufacturing a bracket (10) according to one of the claims 1 to 3, comprising the steps of: curving a flat sheet metal to form said, cylindrical portion (11) having one pair of opposed free edges which face each other with a gap; placing said cylindrical portion (11) within a cavity of a mold, placing an inner sleeve (21) inside of said cylindrical portion (11), filling a space defined by said cylindrical portion (11) and said inner sleeve (21) with a rubber material, and vulcanizing said rubber material so that a vulcanized elastic rubber member (22) is integrally bonded to both an inner surface of said cylindrical portion (11) and an outer surface of said inner sleeve (21) by vulcanization, thereby forming a vulcanized molded body; substantially reducing the diameter of said cylindrical portion (11) of said vulcanized molded body by forcibly bringing said one pair of opposed free edges closed to each other; and integrally securing said metallic arm portion (12) and said one pair of opposed free edges of said cylindrical portion (11) in the diameter-reduced state to each other by welding to form said bracket composed of said cylindrical portion (11) and said arm portion (12). A method according to claim 7, characterized in that said welding is carried out by resistance welding, said outer surface of said cylindrical portion (11) and said metallic arm portion (12) being relatively abutted on each other, and a welding current being fed to abutting faces of said cylindrical portion (11) and said metallic arm portion (12) to be molten into each other. A method according to claim 7, characterized in that said welding is carried out such that the temperature of said cylindrical portion (11) is controlled to 150°C or less upon welding.

Inventors: HANAZAKI MASAHIKO, HIBI MASAYUKI, TAZUKE YUTAKA, HANAZAKI, MASAHIKO, HIBI, MASAYUKI, TAZUKE, YUTAKA, HANAZAKI, MASAHIKO, C/O TOKAI RUBBER IND. LTD., HIBI, MASAYUKI, C/O TOKAI RUBBER IND. LTD., TAZUKE, YUTAKA, C/O TOKAI RUBBER IND. LTD.
Applicants: TOKAI RUBBER IND LTD, TOKAI RUBBER INDUSTRIES, LTD.
Application year: 1994
Main classification: F16F13
IPC codes: F16F13, B23K11, F16F1